The use of medical balloons for dilatation of a body vessel as well as for expansion and seating of a medical devices such as a stent is well known. Medical balloon may be made of a single layer of material or of multiple layers of material. In the case of multilayer balloons, the multiple layers may be of the same or different materials.
A variety of materials have been used for making medical balloons including thermoplastic polyurethanes (TPU), polyethylene, polyesters such as polyethylene terephthalate (PET) including non-compliant PET, Arnitel, Hytrel, polyetherether ketone (PEEK), block copolymers of polyether polymers and polyamides (polyether block amides) such as Pebax® (all grades) available from Elf Atochem North America, block copolymers of polyether and polyester polymers such as Hytrel® available from E.I. DuPont de Nemours & Co. in Wilmington, Del., Teflon®, polyamides such as nylon-11 and nylon-12, block polyimides, polytetrafluoroethylene (PTFE), polyolefins such as polyethylenes (PE) and polypropylenes (PP), synthetic rubbers including SBR and EPDM, as well as other polyolefins and silicone elastomers. For catheter balloons used in coronary angioplasty preferred polymeric substrates are PET, nylon and PE. The specific choice of materials depends on the desired characteristics of the balloon.
Of these materials, PTFE is of interest for use in medical balloons because of its low coefficient of friction, chemical resistance, flexibility and strength. Because of the physical properties of PTFE, however, the material cannot be processed in the same way that conventional thermoplastic elastomers are processed.
The use of polytetrafluoroethylene (PTFE) and expanded PTFE (EPTFE) in implantable medical devices such as balloons has been disclosed in U.S. Pat. Nos. 5,752,934 and 5,868,704 both of which disclose a balloon comprised of a porous EPTFE layer and an elastomeric or inelastic layer. The EPTFE films may serve either as a coat for a balloon or as an integral part of a balloon in the form of an outer layer. The balloons disclosed therein are formed from a helically wound porous EPTFE film. In one example, twenty layers of EPTFE film are used to form the EPTFE portion of the balloon. As a result, these balloons tend to have a large profile.
It is desirable to produce a medical balloon which has some of the properties of a PTFE balloon and yet has a low profile. More specifically, it is a goal of the present invention to provide a non-compliant EPTFE balloon which has a high burst strength and the ability to return to its preinflation diameter following repeated inflation/deflation cycles. To that end, the present invention provides medical balloons having one or more EPTFE layers disposed between an inner balloon material and an outer balloon material.
All US patents and all other published documents mentioned anywhere in this application are incorporated herein by reference in their entirety.